I. Field of the Invention
The present invention relates generally to tactile display apparatus, and, more particularly, to an electromechanical system for selectively displaying and erasing information from a reference surface.
II. Description of the Prior Art
A particularly desirable application for the invention concerns the presentation of the Braille character set for the blind. However, there are numerous other applications for the invention.
For example, a large matrix of tactile display units could be employed to display numbers, letters, and figures as raised patterns in devices that provide viewing screens for the blind. The sighted can also benefit from the invention. For example, tactile display units can be utilized singularly or in groups as displays on operating consoles for limited or low light conditions such as aircraft, mining equipment, and military hardware where the raised patterns can be utilized as nonvisual indicators.
Braille was devised to enable the blind to read alpha-numeric characters and is in the form of a six unit code, where each cell represents a character or symbol. Thus, with a six unit code in each cell, there is a matrix of two columns with three in a column. By employing a six unit code, a maximum of sixty-four combinations can be created for which include the twenty-six letters of the alphabet, the numbers zero and one through nine, and various symbols such as case indicators, punctuation, and so forth.
A tactile display unit of the type which will be described in detail below is one which provides for the raising and lowering of a physical point above a plane of reference in such a manner that the change of state from one position to another, that is, from a raised position to a lowered position, or vice versa, is physically detectable by the sense of touch. Numerous mechanisms have been devised to provide such tactile displays. They have generally been large, complex, cumbersome, and expensive to construct, operate, and maintain. Many have been patented. Typical of patents which disclose such devices utilizing magnetically operable pins or solenoids are Nos. 3,395,247; 3,510,967; 3,592,965; 3,987,438; 4,033,053; 4,178,586; 4,191,945; and 4,194,190. Other typical patents disclose a variety of other mechanisms for achieving a similar result. For example, No. 2,891,324 discloses a mechanism which utilizes piano-like rolls; Nos. 4,044,350 and 4,473,356 disclose piezoelectric reeds; No. 4,586,904 discloses magnetically operable balls; No. 4,215,490 discloses mechanical linkages; No. 4,266,936 discloses bi-metallic latches; and Nos. 4,445,871 and 4,586,903 disclose the use of continuous belts. Because of their complexity, most of these known devices are expensive to manufacture, thereby resulting in an end product with a cost that is prohibitive to many consumers. Also, the power requirements of some of these devices require drive levels that are beyond the capability of most target units without the addition of a supplemental power supply.